Income inequality has risen steadily among all Americans since the 1970s. But the gap between rich and poor has grown the fastest — and is the widest — among Asians, who have displaced blacks as the most economically divided racial group in the United States.

The finding, in a report released Thursday by the Pew Research Center, paints a more complex economic portrait of Asian Americans than is often captured by snapshots showing Asians at the top of the income ladder.

While Asians as a whole rank as the country’s highest-earning group, economic gains for lower-income Asians between 1970 and 2016 trailed far behind those made by their counterparts in other racial and ethnic groups, the report said.

“Asians are often depicted as the highest-achieving group in America, but it’s clear they are the most economically divided, with a significant share of Asian Americans lagging well behind lower-income whites,” said Rakesh Kochhar, a senior researcher at Pew.

Rising inequality among Asians, the country’s fastest-growing minority, can be largely explained by immigration patterns and the diverse reasons immigrants from an array of Asian countries settle in the United States, Kochhar said.

Immigrants, largely from China, India, Korea, the Philippines and Vietnam, accounted for 81 percent of the growth in the Asian adult population between 1970 and 2016. Nearly 80 percent of Asian adults in 2016 were foreign-born, compared with 45 percent in 1970.

Asian immigration surged after the 1965 Immigration and Nationality Act, which favored family reunification. The end of the Vietnam War in 1975 brought a wave of refugees. One result, the report said, was that the share of new Asian immigrants working in higher-paid, high-skilled jobs dropped between 1970 and 1990.

A new wave of Asian immigrants came to the country after the 1990 Immigration Act that sought skilled workers during the tech boom. Many of the latest arrivals came from India, initially under the high-skilled H−1B visa program.

“Asian Americans come from a wide range of countries and cultures with different assimilation trajectories,” Kochhar said.

Three-quarters of Indian adults in the United States have at least a college degree, compared with less than a third of Vietnamese, less than a fifth of Laotians and Cambodians, and about half of Chinese, Pakistanis and Filipinos.

Median household income varies from $100,000 among Indians to $36,000 among Burmese. Poverty rates among Asians are as high as 35 percent among Burmese and 33 percent among Bhutanese.

Income distribution among Asians has gone from being one of the most equal in the United States to being the most unequal over the past five decades, the report said. During that time, the gap in the standard of living between Asians near the top and the bottom of the income ladder nearly doubled.

In 2016, Asians in the top 10 percent of income distribution earned nearly 10.7 times as much as Asians in the bottom 10 percent. In 1970, the wealthiest Asians earned 6.1 times as much as the poorest Asians.

Among all Americans in 2016, the wealthiest earned 8.7 times as much as the poorest — a steady but more moderate increase in the wealth gap from 1970, when the wealthiest Americans earned 6.9 times as much as the poorest.

The income of the highest-earning Asians — those in the top 10 percent — nearly doubled from 1970 to 2016 to $133,529, the most of any group. Asians in the bottom 10 percent increased their earnings by only 11 percent during this time to $12,478 — less than the earnings of lower-income whites, who made $15,094 in 2016.

But researchers do not expect the gaping income divide among Asians to last, because of changing immigration patterns.

“You will eventually end up with a more settled native-born Asian American population,” Kochhar said, “so the rapid rise in inequality in this population may be a transitory story.”